A standard electrofilter for removing liquid or solid particles from a gas stream comprises a plurality of parallel, longitudinally straight and throughoing, and transversely spaced longitudinal main beams from which are suspended respective parallel and transversely spaced longitudinal main plates. Thus these plates form longitudinally extending and vertically open slots in which are hung longitudinally spaced electrode wires. Opposite charges are applied to the plates and the wires to form a charge zone so that particles in a gas stream normally passed up through these slots become charged and adhere to the surfaces of the plates.
The disadvantage of such an arrangement is that there is relatively little collection surface area. Furthermore the charge density varies greatly, being ample close to the wire electrodes but being quite weak midway between adjacent wires against one side or the other of the slot. Thus such an electrofilter can let pass substantial particles.
It is also known to provide such a filter with a plurality of parallel and longitudinally spaced cross plates that bridge and extending between the main plates at about 90.degree. to define a plurality of square, that is four-sided corners therewith. This increases the surface area for particle collection substantially, but still has dead regions in the corners of the passages where the charge is so very weak that little filtering takes place.
A partial solution to this low-efficiency problem (see German patent documents 1,001,240 and 2,641,114) is the use of a honeycomb arrangement, that is one where the passages are hexagonal in section. In such an arrangement the charge concentration remains high even in the six corners of the passages, but several other problems exist. Principally the problem is that such a structure requires that adjacent passage be staggered with one another if both faces of the passage-defining plates are to be used for particle collection. Thus in and arrangement where both faces of the wall-defining plates are used as collection surfaces thesee walls must deflect back and forth at 120.degree. so that they and their supporting beams cannot be straight. As a result it is impossible to make them as strong as straight beams and planar plates. Since it is standard to make these walls of a lead-coated steel or synthetic resin, or even of solid lead to avoid corrosion when the system is used in a wet-scrubbing system to get rid of sulfur compounds, these wall plates are very heavy. The only solution in the honeycomb arrangement is therefore to align the passages with one another, in which case a large percentage of the usable surface area becomes unusable dead space for a significant and normally intolerable loss in efficiency due in part to the presence of all this dead space and in part to not using both faces of the passage-defining plates.